Simplify the following expression: $t = \dfrac{9k}{4} + \dfrac{k}{7}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $7$ $\lcm(4, 7) = 28$ $ t = \dfrac{7}{7} \cdot \dfrac{9k}{4} + \dfrac{4}{4} \cdot \dfrac{k}{7} $ $t = \dfrac{63k}{28} + \dfrac{4k}{28}$ $t = \dfrac{63k +4k}{28}$ $t = \dfrac{67k}{28}$